Chromatography comprises a group of methods for separating a mixture of substances into their component parts. "Chromatography" is, however, a misnomer for these methods because the color of components is rarely the basis used for identifying and isolating component parts in modern techniques. Traditionally, chromatographic techniques include gas chromatography (GC) or gas-liquid chromatography (GLC), thin layer chromatography (TLC), and column chromatography, frequently called high-performance liquid chromatography (HPLC).
Column chromatography may be used to separate and identify a variety of substances, including pharmaceutical drugs, hormones, and cell constituents including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Generally, column chromatography is a selective filtration or elution process whereby a substance or species to be chromatographed is dissolved or suspended in an eluant and passed through a porous or semi-porous bed or column of chromatographic separation material, from which an eluate may be collected.
The chromatographic separation material is typically chosen dependent upon the substances to be chromatographed. Such separation material may be generally categorized into five types: (1) size-exclusion; (2) affinity; (3) ion-exchange; (4) reversed-phase; and (5) ion pairing. See generally J. A. Thompson, "A Review of High Performance Liquid Chromatography in Nucleic Acids Research," BioChromatography, 1:16 (1986).
Depending upon the nature, density, and height of the column of chromatographic separation material, and the nature of the substance to be chromatographed and the eluants used, pressure may be required (or desired in the interest of time) to force the eluants and substances through the separation material. Conventional techniques include positive pressure, such as a pump or syringe, and negative pressure, such as gravity, vacuum withdrawal or centrifugation. With such a variety of techniques, versatile column chromatography apparatus is often required.
Several manufacturers have produced apparatus for use in column chromatography. For example, Supelco, Inc. manufactures Supelclean Disposal SPE Tubes, which contain silica gel-based bonded phase packings. Solutions may be passed through these tubes into collecting tubes using negative pressure by a vacuum or centrifugation, or by positive pressure by an air pump or syringe. However, the Supelco tube requires a tube adapter to be fitted for a syringe or other positive pressure source using only friction to hold the adapter and positive pressure source in communication with the tube containing the chromatographic material and eluant. Negative pressure by centrifugation is achieved by inserting the column or tube into a collecting tube and inserting this combined unit into a centrifugation device. No locking devices are present.
Sarstedt, Inc. manufactures Microvette.RTM. columns which may be inserted into a collecting tube adapted to receive the Microvette.RTM. columns using friction to hold the columns in place. The Microvette.RTM. column is, however, capable of being twisted even after being inserted into the collecting tube and thus provides no secure means for coupling or uncoupling the Microvette.RTM. columns to insertion apparatus.
Gelman Sciences Inc. manufactures filtration products for high-pressure liquid chromatography adapted to receive substances suspended in an eluant from an insertion device, such as a syringe. The Gelman devices use filters which also function as a coupling between the collecting tube and the insertion source, typically a syringe. The coupling is achieve by friction, but may be locked in place by means of an additional, external clamping device.
CooperBiomedical, Inc. manufactures a mini-spin column comprising a separation material-filled column and a collecting tube adapted to receive and hold in place the column by friction means. The column is not, however, adapted for coupling to an insertion means, such as a syringe. Further, nothing prohibits the column once inserted into the receiving collecting tube from rotating. The column contains one fibrous filter packed into the lower, tapered end of the column on top of which the bed of separation material is packed.
Apparatus made by companies including those listed above are used to chromatograph a variety of substances, including highly toxic or virulent substances. Conventional apparatus generally require that the operator or technician employing the chromatography apparatus come in contact with the apparatus during use. For example, to remove a chromatography column from a collecting tube normally requires one to pull the tube out by hand or by using clamp-like instruments. Similarly, to place a conventional chromatography column coupled to a syringe, for example, into a collecting tube, uncouple the syringe and leave the column in the tube, one must normally hold the chromatography colummn in place to prevent the column from twisting or pulling out while the syringe is removed. Such contact places the operator or technician at risk of touching possibly toxic or virulent chemicals, drugs and genetic material. Recent research into the acquired immune deficiency syndrome (AIDS) virus is one example of genetic material which presents a deadly threat to chromatography technicians. Nothing in the prior art discloses or suggests apparatus which may be used in column chromatography while minimizing risk of exposure to the substances contained therein.
In view of the serious deficiencies and inefficiencies of the prior art, it would be desirable to have an apparatus which minimizes risk of exposure to substances contained therein, which is easy to use, and which is relatively simple and inexpensive to produce.